Traffic direction control for coded track circuit signaling systems



T. J. JUDGE TRAFFIC DIRECTION CONTROL FOR CODED TRACK Nov. 4, 1952 CIRCUIT SIGNALING SYSTEMS 7 Sheets-Sheet 2 Filed Aug. 15, 1946 FIG.2A.

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HIfi ATTORNEY T. J. JUDGE TRAFFIC DIRECTION CONTROL FOR CODED TRACK Nov. 4, 1952 CIRCUIT SIGNALING SYSTEMS 7 Sheets-Sheet 3 Filed Aug. 15, 1946 OOO 3FP BP m i i I 151 I H15 /4 TTORNEY Nov. 4, 1952 'r. J. JUDGE v TRAFFIC DIRECTION CONTROL FOR CODED TRACK CIRCUIT SIGNALING SYSTEMS 7 Sheets-Sheet 4 Filed Aug. 15, 1946 FIG.2C.

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T. J. JUDGE TRAFFIC DIRECTION CONTROL FOR CODED TRACK CIRCUIT SIGNALING SYSTEMS Filed Aug. 15, 1946 7 Sheets-Sheet 5 FIG. 2D.

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HIS r9 TTORNEY T. J. JUDGE Nov. 4, 1952 2,617,014 TRAFFIC DIRECTION CONTROL. FOR CODED TRACK I CIRCUIT SIGNALING SYSTEMS 7 Sheets-Sheet 6 Filed Aug. 15, 1946 IN V EN TOR.

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HIS ATTORNEY T. J. JUDGE Nov. 4, 1952 TRAFFIC DIRECTION CONTROL FOR CODED TRACK CIRCUIT SIGNALING SYSTEMS Filed Aug. 15, 1946 '7 Sheets-Sheet 7 Patented Nov. 4, 1952 TRAFFIC DIRECTION CONTROL FOR CODED TRACK CIRCUIT SIGNALING SYSTEMS Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application August 15, 1946, Serial No. 690,619

14 Claims.

1 This invention relates to coded track circuit signalling systems for railroads, and it more particularly pertains to improvements in coded track circuit signallingsystems of the character disclosed in my prior Patent No. 2,357,519, dated September 5, 1944.

The present invention provides for the control of trafllc through a stretch of single track by an operator at a. remote control oflice', track switch and signal and traffic direction apparatus located at the ends of the stretch being preferably controlledv from the control ofiice by a code communication system. Thus, according to the general organization of the system, the signals at the ends of the stretch are governed from the control oliice,

subject to automatic coded track circuit control dependent upon the condition of occupancy by a train of various blocks, or track sections, in advance of the signals. The switch and signal control apparatus located at each end of the stretch is said to be located at afield station, and each fieldstation is connected to a centralized tra'fiic control line circuit extending to the control office as a part of the code communication system. The signals governing entrance to-the stretch for both directions of trafiic, as well as intermediate signals in the stretch, are governed by distinctive driven codes transmitted through the track rails tosuch signals, and at times inverse, or "off codes-are transmitted from the exit ends of certain of the track sections for use in the provision of approach control.

An object of the present invention is to provide an improved means for reversing the direction of trailic established througha stretch of track in response to the manual designation by an operator at the control oflice of a change in traffic direction, such reversal in direction being accomplished without the use of inverse codes, as the inverse codes are required for approach control purposes.

Generally speakingandwithout attemptingto define the scope of the present invention, the coded track circuits remain coding after the passage of a train for the last established directionof traflic, and a change in thed-irection of trafiic is initiated by an operator at the. control ofiice by the-rotation and depression of a traffic I system to transmit a control to the field station at the entrance end of the stretch, according to 2 the last established traific directionior rendering the track circuit code transmitting apparatus at that end active to apply steady energy to the track rails as a distinctive track circuit control for shifting trafiic direction relays at the next signal location in advance, and thus render the steady energizationof the respective blocks in advance successively through the entire stretch of track to prove that the stretch is unoccupied by a train.

The reception of the steady energization in the track rails at the field station at the opposite end of the stretch proves that the stretch is unoccupied by a train and transmits such indication to the control oihce. The reception at the control office of the indication that the stretch is unoccupied automatically initiates the code communication system into a cycle of operation for transmission of a code to the entrance end of the stretch, according to the previously established direction of trailic, to remove the steady energy from the track rails at that end and start the transmission of driven codes through the respective track sections to establish the new direction of trafiic.

Another objectoi the present invention is to so arrange the trafiic direction control organization at the ends of the blocks that the last established direction of traflic is maintained by magneticsticlc relays in case of an interruption of power.

Another object of the present invention is to provide a means by which signals governing traffic through a stretch of track are maintained atstop if a change in traffic direction is initiated without being manually designated by the dispatcher, such, for example, as by a signal maintainer applying. steady energy across the track rails in testing.

Another object of the present invention is to indicate at the control ofiice an outof-correspondence condition between the manual traffic direction designation means and the condition of the traiiic direction control apparatus in the field,

' and thus indicate to the dispatcher any condition where a change in trafiic direction which has been initiated cannotbe completed.

Another object of the present invention is to provide a trafiic-dire'ction control system in which no signal can be cleared, either automatically or by any act of the dispatcher, for anewly designated traffic direction if a train is occupying any track section Within'the limits of the stretch of track subject to traffic-direction control.

Other objects, purposes, and characteristic features of the present-invention will be in part obvious from the accompanying drawingsand' in 3 part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings in which those parts having similar features and functions are designated through the several illustrations by like letter reference characters which are generally made distinctive by reason of preceding numerals indicative of the particular function with which such parts are associated, and in which:

Fig. 1 illustrates control ofiice apparatus for the transmission and reception of respective controls and indications by a code communication system;

Figs. 2A through 2D when placed side by side respectively illustrate the circuits employed for the control of signals and traffic direction control apparatus of this embodiment of the present invention;

Figs. 3A through 315] illustrate by track diagrams the general mode of operation of the system provided by the present invention upon the passage of a train; and,

Figs. 4A through 4G illustrate by track diagrams the general mode of operation of the system upon reversing the direction of traffic.

The illustrations employed in the disclosure of this embodiment of the present invention are arranged as schematic wiring diagrams for the purpose of facilitating the disclosure as to the mode of operation and principles involved in the system without attempting to illustrate the specific construction and arrangement of parts that would be employed in practice. Thus, the relays and their contacts are shown in a conventional manner, certain relays being shown in block form only and reference bein made to the prior art for a more detailed disclosure as to their mode of operation. Rather than illustrate all sources of energy in detail, the symbols and are employed to indicate the respective positive and negative terminals of a suitable source of direction current.

The signal symbols used in the diagrams of Figs. 3A through 3E and 4A through 1G are to be considered as indicative of the indications of the signals rather than the type of signals employed, the signals employed in this embodiment of the present invention being of the color light type having individual color light units.

In order to simplify the description of the present invention, a general reference is made from time to time to functions common to all parts having similar functions by use of letter reference characters without their preceding numerals, and such references to be considered as applicable to any apparatus falling into such classification, irrespective of the numerals preceding the letter reference characters of such apparatus.

The trackway for this embodiment of the present invention as illustrated in Figs. 2A through 2D, is divided into blocks, each block having an entering signal for each direction of traffic. For simplification of the present disclosure, only a single track section is included in each block, but it is to be understood that more than one track section can be employed in accordance with the requirements of practice. It is also to be understood that the track layout employed in this embodiment of the present invention is to be considered as a typical and simplified track layout to facilitate the disclosure of the present invention. and that the system is readily adapt- 4 able to track layouts of a modified nature having difierent number of track sections and signals involved.

The arrangement of the signals at the ends of the single track stretch is provided in accordance with the usual practice in centralized traffic control whereby an OS detector track section is provided for a track switch at each end of each passing siding such as the track section i-2'I at the right-hand end of the passing siding A, and the track section 'l-BT at the lefthand end of the passing siding B. The stretch of single track extending between the passing sidings A and B is illustrated as divided into the three track sections 2-3T, 4-51, and 6-11.

The signals employed in this embodiment of the present invention are of the color light type having individual color light units for providing respective stop, caution and clear indications in accordance with the illumination of red, yellow and green lamps. It is to be understood, however, that other types of signals, such as searchlight signals, semaphore signals or position light signals could as well be employed in accordance with the requirements of practice.

The arrangement of the signals is such that the signals 2A and 2B are provided for governing entrance to the stretch of single track at the left-hand end of the stretch, and the signals 7A and 1B are provided for governing entrance to the stretch of track at the right-hand end. The signals IA and IB, and 8A and 8B are leaving signals with respect to traffic through said stretch at the respective left-hand and right-hand ends of the stretch. All signals at the ends of the stretch are subject to the control of a dispatcher at the control oflice as well as the automatic control through the track circuits, and thus such signals are normally at stop in accordance with the usual practice in centralized trafiic control systems.

The automatic signals 4 and 6 are provided for governing entrance to the track sections l-ET and B-IT respectively for east bound traffic, and the signals 3 and 5 are provided for governing entrance to the track sections 2-3T and 45T respectively for West bound trafiic. The control of such signals is automatic in accordance with track circuit codes transmitted through the track rails of the track sections in advance.

Each of the track sections in the stretch of track between the passing sidings A and B has a coded track circuit which includes a track battery and a code following track relay TR at each end of that track section. For the purpose of obtaining the best operating conditions of each code following track relay, it is desirable that such relay be of the biased polar type having a polar structure so arranged as to cause the relay contacts to be biased to a deenergized position from which they can be moved only upon energization of the relay windings with a particular polarity.

A code transmitter relay CP is provided at each end of each of the track sections having a coded track circuit for the transmission of track circuit codes, such relay being effective when rendered active to transmit code pulses formed by suitable code oscillators, or other code pulse forming means, at a or '75 code rate. A suitable code oscillator is shown, for example, in the patent to O. S. Field, No. 2,351,588, dated June 20, 1944. It is preferable that each of the code transmitter relays CP be of the biased polar type to provide improved operating characteristics, particularly where such relays are used for the transmission of inverse codes.

Code receiving means responsive to the pulsing of the track relay TR at each end of each of the track sections having a coded track circuit com.- prising a track repeater relay TP, which is a code following relay, a front contact repmter relay FP sufficiently slow acting to be maintained steadily picked up in accordance with the pulsing of the associated track relay TR, a front-back repeater relay FBP which is sufiiciently slow acting' to be maintained steadily picked up upon the reception of a track circuit code by the associated relay TR, a decoding transformer, a slow acting relay H energized by the decoding transformer so as to be maintained steadily picked up upon the reception of a track circuit code, and a distant control relay D energized from the decoding transformer through a tuned circuit and rectifier IBODU so as to be steadily picked up only in response to a 180 code. For the purpose of reducing to a minimum the equipment required at the intermediate signal locations, certain of the above-described code receiving apparatus is selectively controlled so as to be employed for both directions of trafiic. Thus, at each intermediate signal location, the relays TP, H and D are selectively controlled to be associated with either track section at such intermediate signal location.

A relay TPA is provided at intermediate signal locations as required for the transmission of inverse code pulses, a single relay TPA being selected to be used for both directions of traflic' at an. intermediate signal location for cooperating with a track relay TR to determine the length of the inverse code pulses transmitted from that signal location.

A traffic direction relay FR is provided at each end of the stretch of single track and at each intermediate signal location for the purpose of selecting the control of the above described code transmitting and receiving apparatus in accordance with trafiic direction designated by a dispatcher at the control office. Each relay FR, is of the two position magnetic-stick type which. is characterized by maintaining its contacts in its last operated position until energy of the opposite polarity is applied to that relay. By using a relay having these characteristics for tratfic direction control, the last. established direction is always maintained in case of a power interruption. In additionto the traflic direction control relay E-SFR (see Fig. 2C) for the typical intermediate location illustrated, a slow pick up directional stick relay E-EFS is provided for governing code transmission. This relay permits the transmission of track circuit code in one track section, provided that a track circuit code is being received through the track rails of the ad-joining'track sectionQ Another slowpick up relay S-SFC is provided at the typical intermediate signal location illustrated in Fig. 2Cf0r cooperating with the magnetic stick relay 5-6FR upon changing the direction of trafiic.

Although the apparatus associated with the code communication of switch and signal and trafiic control from the control office to the respective field stations, and the transmission of indications from such field stations to the control ofiice as to the conditions of the apparatus, is not fully disclosed in the drawings, reference is to be made for a complete disclosure of such apparatus to the prior application of Hailes et al.,

Ser. No. 484,728, dated April 27, 1943, which has resulted in Patent No. 2,399,734, dated May 7, 1946. The parts of the code communication system shown in the accompanying drawings have been arranged to cooperate with the system disclosed in that Hailes et a1. application, although it is to be understood that other types of code communication systems can as well be employed.

With reference to Fig. 1, certain parts of the control machine at the control ofiice are illustrated comprising a miniature diagram of the track layout for which this embodiment of the invention is provided, such diagram having associated therewith OS track indicator lamps l-ZTE and 'l-8TE for the OS track sections at the respective left-hand and right-hand ends of. the stretch of single track, and the lamps ZAE'and; TAE for indicating the approach of trains to the respective left-hand and right-hand ends, cat the stretch.

Trafiic direction control button l-BFB is conveniently located near the miniature track diagram for controlling the direction of traific through the stretch. The button l--8FB that. is illustrated is of the rotary type having an arrow included in the button for indicating the direc tion of trafiic. The button l-8FB is operable by rotation through to change the direction of traffic,- and it also has contacts closed upon the depression of the button, such contacts being used in initiating the transmission of a control by the code communication system for causing a change in the direction of traffic. The traific direction button l-8FB can be, for example, of the general character disclosed in patent to J. F. Merkel, Patent No. 2,305,185, dated December 15, 1942. It is to be understood that various other types of manually operable control buttons or levers could as well be employed in. accordance with the requirements of practice.

The out-of-correspondence lamp CFK, which is energized when the trafic direction arrow of the button l-8FB is out of correspondence with the direction of traffic actually established in the field, is preferably mounted in the rear of. the button l-BFB for causing the illumination of the center portion of that button when such lamp is energized.

The slow acting relays CH2 and CH3. are change, or start, relays for'the transmission of switch and signal and trafiic direction controls to the respective field stations No. 2 and No. 3, and the picking up. of either of such relays-causes the picking up of an associated relay for connecting the respective channels of the code communication system to control code determining relays SL and LS as selected by switch and signal and traffic direction control contacts.

A traffic locking relay l-BFL of the magneticstick type is provided at the control ofiice for the purpose of allowing the transmission of controls to the field for a change in the direction out trafiio only if the signals governing entranceat the respective ends of the stretch are indicated at thecontrol ofiice as being at stop.

A relay FPS is provided at the control ofiice for each end of the stretch for use in connection with the mode of operation of the system. upon the reversal in the direction of trafdc'. Such relay is of the neutral type and is maintained picked up only by energization of its pickup or stick circuit.

The magnetic-stick relays l-ZGK, ZFK, ZAK and l-2TK are conditioned in accordance with the reception of indications communicated from the field station No. 2 to the control ofiice. Similarly, the relays 'l-SGK, SFK, 'IAK and 'I-BTK are of the magnetic-stick type and are conditioned in accordance with the communication of indications from the field station No. 3 to the control office.

The part of the code communication system located at field station No. 2 for the reception of controls and the transmission of indications is indicated in block form in Fig. 2A as reference is to be made to the above-mentioned application of Hailes et al. for a complete disclosure as to the organization of such apparatus. Thus, for the purpose of disclosure of the present invention, it is assumed that the relay ZRGZ is picked up at the field station No. 2 in response to the transmission of a control from the control ofiice for clearing a signal governing traffic to the right, and similarly, the relay ZLGZ is picked up in response to the transmission of a control from the control oflice for clearing a signal governing traific to the left. The relay l-2B is responsive only to the transmission of a code from the control office for restoration of a signal at field station No. 2 to stop.

The traffic control relay 2FZ is of the magnetic-stick type and it is controlled through the medium of the code communication system from the control office in a manner to be more readily understood as the description progresses.

It is to be understood that a similar arrangement of apparatus to that which has been described as associated with field station No. 2 is provided at field station No. 3. Thus, with reference to Fig. 2D, the relays 3RGZ and 3LGZ are responsive to control codes transmitted from the control ofilce for clearing signals governing east bound and west bound trafiic respectively, and the magnetic-stick relay 'IFZ is conditioned from the control oflice as required in the control of the establishment of traffic direction.

According to usual practice in centralized traffic control systems, each of the track switches W has associated therewith respective normal and reverse switch correspondence relays NCR. and RCR. These relays are energized only when the associated track switch is in its respective normal or reverse position in correspondence with the switch position that has been last called for by the code communication system. Thus, the relays ZNCR and 23GB. (see Fig. 2A) are associated with the track switch 2W, and the relays 3NCR and 3RCR are associated with the track switch 3W.

Having thus considered the general structural organization of the system, it is believed that an understanding of the circuit organization can best be understood by a consideration of various typical operating conditions of the system to be encountered in practice.

Operation GeneraZ.-A consideration of the general mode of operation of the system before making specific reference to the circuit organization for providing such mode of operation will be considered with reference to the track diagrams of Figs. 3A through 3E, and Figs. 4A through 4G.

With reference to Fig. 3A, the conditions hereinafter referred to as the normal conditions of the system are illustrated in which the direction of track circuit code transmission is maintained in accordance with the last established direction of traiilc for the passage of east bound trains.

Under the normal conditions of the system the signals associated with the respective field stations No. 2 and No. 3 are at stop, and thus in accordance with signal 8A being at stop, and the last direction of trafiic being established for east bound trains, a '75 driven code is transmitted from right to left in the track section B-lT to provide a control for the intermediate signal 6 to cause that signal to indicate caution. With the signal 6 at caution, a driven code is transmitted from right to left in the track section 4-5T in the rear of that signal to cause the signal 4 to be clear. In accordance with the clear indication of signal 4, a 180 driven code is transmitted from right to left in the track section 2-3T in the rear of that signal to provide a means for clearing the signal 2A, or the signal 23, if a control is communicated from the control office for the clearing of either of such signals. It will be noted that an inverse code is shown as being transmitted from left to right in the track sections 4-5T and 6-1T for the purpose of providing approach control for the signals 8A and 83.

With reference to Fig. 3B, it is assumed that a control is communicated from the control oflice for the clearing of a signal at field station No. 2 for governing trafific to the right, with the track switch 2W in its normal position. The reception of such control at field station No. 2 causes the picking up of the relay ZRGZ, and the picking up of that relay, allows the signal 2A to clear in accordance with the reception of the 180 driven code transmitted from right to left in the track section 2-3T in advance of that signal.

With reference to Fig. 30, it is assumed that an east bound train has accepted the signal 2A, and the passage of such train has caused the restoration of the signal 2A to stop and the dropping away of the signal control relay 2RGZ, thus requiring the transmission of another control from the control ofiice for again clearing the signal 2A for a following train. It has been assumed that the dispatcher at the control ofiice has transmitted a control to the field station No. 3 for the clearing of signal 8A, thus causing the picking up of the relay BRGZ at that field station and the clearing of signal 8A, assuming that a route has been established sufiiciently in advance of that signal so that a 180 driven code is transmitted from right to left in the track section 8-9T for the clearing of that signal. Upon the clearing of signal 8A, the code rate is conditioned to be increased in the track section 6-71 from a 75 to a 180 code, but such increase can actually become effective only in the absence of inverse code in that track section.

Further progress of the east bound train is illustrated in Fig. 3D in which it is assumed that the train has entered the track section 4-5T and by entering such track section has caused a tumbledown of the inverse code through the track sections d-ET and 6-H to provide for the dropping away of the approach control relay AAR. The removal of the inverse code from track section 6-7T allows the increase in code rate in that track section to a 180 code.

With reference to Fig. 3E, the east bound train is assumed to have progressed to a point to occupy the track section E-lT, with the track section 4-51 becoming unoccupied in the rear of the train to provide for the transmission of a 75 driven code from right to left in the track section 4-51 and the reestablishment of inverse code in that track section. As the train progresses further so as to leave the stretch of track between the passing sidings A and B, and leaves the OS track section 'I-8T, the conditions of the signals and of track circuit code transmission are restored to the normal conditions illustrated in Fig. 3A.

With reference to Fig. 4A, the initial step is illustrated in the reversal in the direction of traflic throughthe stretch of track between the passing sidings A and B. This diagram illustrates that a dispatcher at the control ofiice has caused the communication of a traffic direction change to field station No. 2 so as to cause the picking up of the magnetic-stick relay ZFZ. In accordance with the picking up of relay 2FZ a sequence of relay operations takes place by which steady energization is applied to the track rails at the left-hand. end of the track section 2-3T to render the driven code transmitter inactive at the right-hand end of that track section.

With reference to Fig. 43, it is illustrated that the reception of the condition of steady energization at the right-hand end of the track section 2-3T has become effective to operate the contacts of the magnetic-stick relay 34FR to their left-hand positions and thereby initiate the steady energization of the track rails of the track section 4-5T to suppress the transmission of driven codes at the right-hand end of that track section.

With reference to Fig. 4C, it is illustrated that the trafiic direction relay 5-6FR has operated its contacts to their left-hand positions in accordance with the reception of steady energization at the right-hand end of the track section 4-5T, and such operation is illustrated as having been eifective to apply steady energy to the track rails at the left-hand end of track section 6-IT.

With reference to Fig. 4D, it is illustrated that the reception of steady energy at the right-hand end of the track section B-TT is efiective to cause the relay 8-9FR to operate its polar contacts to their left-hand positions to complete the chain of events to check that the stretch of track between the passing sidingsA and B is unoccupied by a train. In response to the shifting of the contacts of the relay B-SFR, an indication is automatically transmitted to the control ofiice of a change in the position of the contacts of that relay.

'With reference to Fig. 4E, it is assumed that the control ofiice has received the indication that the stretchof track is unoccupied between the passing sidings A and B, and in response to the reception of that indication, the apparatus at the'control office is automatically initiated into a cycle of operation for transmission of a control to the field station No. 2 for causing the restoration of relay ZFZ to its dropped away position, and thus remove the condition of steady energization which has been applied to the track section 2-31 with the relay ZFZ in its picked up position. The combination of the relay ZFZ dropped away and the relay ZFR with its polar contacts in their left-hand positions, provides a selection which is elfective to render the driven code transmitter at field station No. 2 active for the transmission of a driven code at a selected rate from left to right in the track section 2-3T. Thus,- assuming the signals IA and IE to be at stop, a 75 driven code is transmitted from left to right in the track section 2-3T, and the reception of that code at the right-hand end of that track section is eiiective to cause the picking up of the code responsive relay SFBP.

' With reference to Fig. 4F, because of the picking up of the relay SFBP in response to the driven code transmitted from left to right in the track section 2-3I', the track circuit code transmitter at the left-hand end of the track section 4-5T is rendered active to transmit a driven code, and the reception of such code at the righthand end of the track section 4-5T causes the picking up of the code responsive relay GFBP. Upon the reception of the code at the right-hand end of the track section 4-5T, the inverse code is established in that track section, and the reception of such inverse code at the left-hand end of that track section is eflective to start the transmission of an inverse code in the track section 2-3T.

With reference to Fig. 4G, a condition is illustrated in which it is assumed that the picking up of the relay GFBP has been effective to initiate the transmission of a 180 driven code in the track section 6-1T to cause the picking up of the code responsive relay 'IFBP at the right-hand end of that track section and thus complete the establishment of driven code through the stretch of single track between the passing sidings A and B. The conditions thus established as illustrated in Fig. 4G will be readily recognized as comparable to the conditions illustrated in Fig. 3A and described as the normal conditions of the system except that such conditions are set up for the opposite direction of traflic.

Normal conditions-With reference to Fig. l, the normal conditions at the control ofiice are considered to be those illustrated in which the signal control levers l-2SGL and 'I-8SGL are in their center positions, corresponding to the stop indications of the signals with which they are associated; and the relays associated with the communication of control codes to the field stations are normally deenergized, corresponding to the at rest conditions of the code communication system when it is inactive for the transmission of controls to the field stations.

The magnetic-stick relays ZFK and 3FK are positioned with their contacts operated to their right-hand positions in accordance with indications assumed to have been communicated to the control ofiice from the respective field stations No. 2 and 3 in accordance with the last established direction of tramc.

The relay ZFPS is maintained picked up by its stick circuit in accordance with the east bound direction of traffic established, such stick circuit extending from including front contact. .20 of relay 2FPS, polar contact 2| of relay ZFK in its right-hand position, and winding of relay ZFPS, to

At the field stations, the relays which are illustrated as being controlled by the code communication system are normally deenergized, and the relays F2 are assumed to have been last positioned so as to have their armatures operated to lower, or dropped away positions.

, Each of the trafiic direction relays FR in the field has its polar contacts operated to their right-hand positions in accordance with the last established direction of traflic to select the control of the track circuit code transmitting and receiving apparatus to establish track circuit codes transmitted in directions as shown in Fig. 4A, and as has been heretofor considered in a general manner.

The relay 'ICP (see Fig. 2D) is active to transmit a '75 driven code by its energization for each pulse created by the oscillator contact 150. The

circuit by which relay 'ICP is active extends from including back contact 22 of relay 'I'TR, oscillator contact 156, front contact 23 of relay lFBP, back contact 2L! of relay TFZ, polar contac 25 of relay lFR in its right-hand position, front contact 28 of the approach stick relay TAS, and winding of relay 'ICP, to The pulsing' of contact 2? of relay lCP alternately connects the track battery 28 and the track relay TTR across the track rails at the right-hand end of the track section B-lT.

The reception of each driven code pulse at the left-hand end of the track section 6-1T energizes the relay ETR (see Fig. 20) through the back contact 2's of relay ECP, and the pulsing of front contact 313 of the relay 6TB causes the relay 6F]? to be maintained steadily picked up. With the relay 5F? picked up, the pulsing of back contract 30 of relay 6TB, maintains the relay BFBP steadily picked up by a circuit including front contact 3| of relay SFP.

Because of the right-hand position of the contacts of the traffic direction relay E-GFR, the code following track repeater relay 5-STP' is active to repeat the pulsing of the track relay 6TB. Thus, the relay 5-6TP is energized each time the relay 6TB, is picked up by a circuit extending from including front contact 32 of relay BTR, front contact 33 of relay GFBP, polar contact 34 of relay 5-5FR in its right-hand position,

3'! to provide for the direct current energization of the relay 5-51-1. It will be noted that the back contact 33 of relay 5fiFC is included in the control circuit of the relay 5-6H, such contact being included for purposes involving the organization of the system for reversal in the direction of trafiic as will be hereinafter described.

The relay 5-61) is controlled by the decoding transformer 31?, but such relay is dropped away under the conditions which are being considered because of the 75 code rate. Thus, the signal 5 displays a caution indication by the energization of its yellowlamp Y. The circuit for the yellow lamp Y extends from including contact 39 of relay 5-FR in its right-hand position, front contact 6:? of relay S-SH, back contact 4| of relay 545D and the yellow lamp Y of signal 6 to It is selected by the closure of front contact 42 of relay ii-6H that the relay 5GP is active for the transmission of a 180 driven code in the track section 4-5T. The circuit by which relay EC? is active extends from including back contact 53 of relay ETR, front contact 44 of relay LEFS, oscillator contact I896, front contact 42 of relay 5-5H, front contact #15 of relay GFBP, front contact 45 of relay EFP, polar contact 47 of relay 5-6FR in its right-hand position, and winding of relay 5GP. to The pulsing of contact 48 of relay 5GP alternately connects the track battery 49 and the track relay 5TB. across the track rails at the right-hand end of the track 7 section i-5T.

The reception at the left-hand end of the track section ii-5T of the 80 code causes the pulsing of the track relay 4TH (see Fig. 2B) because of such relay being connected across the track rails through the back contact 50 of relay 4GP. The pulsing of contact 5| of relay 6TB, causes the relays 4FP and 4FBP to lie-maintained steadily picked up, and the pulsing of contact 52 provides for the energization of the relay 3-4TP for each pulse of the code received, the circuit for relay 3-4TP including front contact 53 of relay 4FBP and polar contact 54 of relay 3-4FR in its righthand position. In accordance with the'pulsing of contacts 55 and 56 of the relay 3-GTP, at a 180 rate, relay 3-6H is maintained steadily picked up through the decoding transformer, and the relay 34D is energized by the output of the transformer 57 through its tuned circuit and rectifier lBBDU to be maintained steadily picked up.

It is, therefore, provided that the signal 4 has its green lamp energized for providing a clear indication, the circuit for such lamp extending from including polar contact 58 of relay 3-4FR. in its right-hand position, front contact 59 of relay 34H, front contact 69 of relay 3-4D, and the green lamp G of signal 4, to e The relay 3GP is active for the transmission of a 180 code at the right-hand end of the track section 2-3T, as selected by front contact (H of the relay 3-HT. Thus the relay 3GP is energized for each pulse of the oscillator I890 by a circuit extending from including back contact 62 of relay 3TH, front contact 63 of relay 3-4FS, oscillator contact lSllC, front contact 6| of relay t-fiH, front contact 64 of relay 4FBP, front contact 65 of relay lFP, polar contact 66 of relay 3-FR in its right-hand position, and winding of relay 3GP, to

The reception at the left-hand end of the track section 2-3T of the 180 code causes the pulsing of the relay 2TB, (see Fig. 2A) because its winding is connected across the track rails through the back contact 6'. of relay 20?, and the pulsing of contact 68 of relay 2TB, provides for the energization of the relays ZFP and ZFBP. The pulsing of contact 69 of relay 2TR causes the pulsing of the track repeater 2TP, such relay being energized for each pulseiby a circuit extending from including front contact 69 of relay 2TB, front contact 70 of relay ZFBP, polar contact H of relay ZFR in its right-hand position, and winding of relay 2TP, to

The pulsing of contacts '52 and 73 of relay ZTP maintains the relays 2H and 2D picked up, the energization of such relays being eifective only when polar contact 1! of relay EFR is in its right-hand position. Although the relays 2H and 2D are picked up, the signals 2A and 2B are maintained at stop until a control is transmitted from the control office to cause the picking up of the relay ZRGZ.

The relay 6GP (see Fig. 2B) is active to transmit an inverse code from left to right in the track section 4-5T because of its energization for each pulse of the inverse code by a circuit extending from including back contact 52 of relay 4TB, front contact M of relay 3- lFS, front contact 15 of relay lFBP, polar contact 16 of relay 3-4FR in its right-hand position, back contact H of relay S- ETPA, polar contact 18 of relay 3-4FR in its right-hand position, and winding of relay flCP, to

At the same time that the above described circuit for the relay QCP is closed, a circuit is closed for the relay 3-4TPA extending from including back contact 52 of relay 4TB, front con tact M of relay 341 s, front contact 15 of relay QFBP, contact '58 of relay 3-4FR in its right-hand position, the variable inductance I9 and the winding of relay .3-4TPA, to Upon the picking up of the relay 3 -4TPA, the circuit which has been described for the relay 4GP is open to terminate the inverse code pulse. It will be apparent from the circuits which have been described that the inclusion of the variable inductance in series with the winding of the relay 3-4TPA provides a means for adjusting the length of the inverse code pulse.

The reception of the inverse code at the righthand end of the track section 4-5T causes the track relay 5TB. (see Fig. 2G) to follow the code, and the pulsing of contact 8| of that relay provides for maintaining the relays BFP and SFBP picked up. It will be noted that the pulsing of contact 43 of the relay 5TB cannot affect the operation of the relay 5-6TP because of the contact 34 of the relay 5-6FR being in its right-hand position.

The relay GOP is effective to transmit an inverse code from left to right in the track section fi-lT by the energization of a circuit similar to that described for the control of the relay 4GP except that the relay GOP is rendered active only so long as the front contact 82 of the relay 5F? is closed, thus providing a means for providing tumbledown when the inverse code is removed at the left-hand end of the track section l-BT. The circuit for relay 6GP extends from including back contact 32 of relay 6TB, front contact .83 of relay E-EFS, front contact 82 of relay 5FP, front contact 84 of relay 6FBP, contact 85 of relay 5-6FR in its right-hand position, back contact 85 of relay 5-6TPA, contact 81 of relay E-EFR in its right-hand position, and winding of relay 6GP to The reception at the right-hand end of the track section 6-'|T of the inverse code causes the pulsing of the track relay lTR (see Fig. 2D) and the pulsing of contact 88 of such relay maintains the relays 'IFP and TFBP picked up.

The approach control relay BAAR is maintained energized in accordance with the reception of the inverse code by the energization of a circuit extending from including the contact 89 of relay .lFR in its right-hand position, front contact 9a of relay IFP, and winding of relay BAAR, to The closure of front contact 9| of the relay 8AAR is efiective through the CTC communication system to position the magnetic-stick relay 'IAK (see Fig. l) at the control office so as to provide that the indicator lamp IAE controlled by such relay is maintained normally dark.

A front contact of the relay SAAR. in multiple with a front contact of the relay 8BAR is assumed to be included as a release circuit for the approach locking (not shown), such approach locking being provided in accordance with the usual practice, such, for example, as in a manner shown in my prior Patent No. 2,357,519, dated September 5, 1944. More specifically, an approach control relay could be provided for the signal 8 corresponding to the relay BAS shown in Fig. 3 of my prior patent, and the front contacts of relays 8AAR and 8BAR connected in multiple could be used as an approach release in place of the front contact of the relay 8AR as shown in that patent.

At the left-hand end of the stretch of track between the passing sidings A and B, the relay ZBAR. is normally energized in accordance with the reception of the driven code at the left-hand end of track section 2-3T. Relay ZBAR is energized by an obvious circuit in accordance with the closure of front contact 92 of relay 2H, and the energization of that relay is effective to close a release circuit (not shown) for the approach locking of signal IA in a manner comparable to that which has been described with respect to the release circuit for signal 8A. In accordance with the closure of front contact 93 of relay ZBAR, it is provided that the approach indication relay 2AK (see Fig. l) at the control ofiice is energized with a polarity to provide that the approach indicator lamp 2AE is normally dark.

A traffic direction stick relay FS is normally energized at each of the intermediate signal 10- cations by the closure of its stick circuit. Thus; the relay 3-4FS (see Fig. 2B) is maintained picked up by a stick circuit extending from including back contact 94 of relay 3-4FC, front contact 95 of relay 3-4FS, and winding of relay 3-4FS to The relay 5-6FS (see Fig. 2C) is maintained picked up by the energization of a similar circuit closed at back contact 96 of relay 5-6FC. It will be apparent as the description progresses that the relay 3-4FS is maintained picked up until there is a change in traffic direction, and the dropping away of that relay upon a change in tranic direction provides that driven code transmission cannot be rendered effective at that signal location until the reception 'of track circuit code for the new direction of traffic has been effective to pick up the relay H at that signal location.

Passage of a. tmin.Tc consider the mode of operation of the system upon passage of a train,

it will be assumed that the conditions of the system are initially as illustrated in Fig. 3A, and as described when considering the normal conditions of the system with traffic established for the passage of east bound trains. It will be assumed that an east bound train approaches the signal 2A at the left-hand end of the stretch of single track and that an operator at the control o-flice actuates the signal control lever l-2SGL to its right-hand position for causing the clearing of that signal. With reference to Fig. l, the operation of the lever I-ZSGL to its right-hand position closes contacts 9? and 98 of that lever for the respective signal control channels of the code communication system to provide for the transmission of a signal control code to field station No. 2 for the picking up of the relay ZRGZ (see Fig. 2A).

In accordance with the picking up of relay 2RGZ, a circuit is closed for the signal control relay ZAG extending from including front contact 99 of relay i-ZTR, front contact Hill of relay ZNCR, back contact llll of relay ZRCR, polar contact m2 of relay ZFR, in its right-hand position, front contact I 03 of relay ZRGZ, front contact we of relay 2H, and winding of relay ZAG, to Upon the picking up of relay ZAG, the circuit for the red lamp R of signal 2A is opened at back contact I05, and the closure of front contact H35 of relay ZAG provides an obvious circuit for the energization of the green lamp G of signal 2, including front contact H36 of the relay 2D (assuming that such relay to be picked up in response to a driven code in the track section 2-3T).

When the east bound train accepts the signal 2A and enters the OS track section l-2T, the relay ZRGZ is dropped away by the opening of its stick circuit (not shown) in a manner fully disclosed in the above-mentioned patent to Hailes et al. The dropping away of the OS track relay I -2TR causes the dropping away of the relay EAG to open the circuit for the green lamp G of signal 2A and 15 closes a circuit for the red lamp R of that signal. The dropping away of relay i-ZTR also closes back contact Hl'l for the transmission of an indication by the code communication system to the control office that the track section l-2T has become occupied by the train,

The shunting of the track section Z-BT as the train progresses causes the dropping away of the relays ZFP, ZFBP, 2H and 2D, when the track relay 2TB is rendered inactive, and the dropping away of relay 2H opens the circuit for the relay ZBAR to cause that relay to be dropped away. Upon the dropping away of the relay ZBAR under such conditions, with the relay 2AAR dropped away at that time, provides that an indication is transmitted by the code communication system to the control office that the train has entered the track section Z-ST. Such indication is communicated to the control oiiice because of the front contacts 93 and 588 of relays ZAAR and ZBAR being open.

Assuming further progress of the train, the entrance of the train into the track section 6-5T causes the dropping away of relays iFP, @FBP, 34H and 3-4D because of the track relay dT-R being rendered inactive, and the dropping away of relay 3-4H opens the circuit for the green lamp of signal 4 and closes an obvious circuit at back contact 59 for the red lamp R of that signal. In

accordance with the dropping away of relay E-I-I,

the shifting of contact SI of that relay changes the code transmitted by the relay 3GP from a 180 code to a 75 code by the inclusion of the oscillator contact 150 in the circuit for relay 3GP in place of the oscillator contact I860.

The presence of the train in the track section 4-5T causes the removal of inverse code from the track section d-BT in an obvious manner, and thus the relays 5FP and EFBP at the right-hand end of track section 4-5T are dropped away. The dropping away of relay 5FP renders the relay BOP inactive for the transmission of an inverse code in the track section 6-7T by opening the circuit for that relay at front contact 82. Thus, the relays FFP and TFBP are dropped away at the right-hand end of the track section %'IT, and the dropping away of relay BAAR upon the opening of front contact 90 of relay 'IFP is effective to render the approach control effective for the signal 8A in a manner which has been described. Because of the front contacts 91 and I89 of relays 8BAR and SAAB, being open at the same time, an indication is transmitted to the control ofiice that the east bound train is in approach of the signals 8A and 8B.

When the track section 2-3T becomes unoccupied in the rear of the train, the transmission of a 75 driven code from right to left in that track section causes the relay 21-1 to be again picked up, and the picking up of such relay causes the picking up of relay ZBAR upon the closure of front contact 92. The closure of front contact 93 of relay ZBAR causes the transmission of an indication to the control oflice that the track section 2-3T has become unoccupied in the rear of the train.

Considering further passage of the train, a similar mode of operation is effective upon the entrance of the train into the track section (i-IT as has been described upon considering entrance of the train into the track section 4-5T, the shifting of contact 42 upon the dropping away of the relay 5-61-1 being efiective to select a 75 code for transmission through the track section 4-5'1 to provide for the picking up of relay 34H when the track section 4-51 becomes unoccupied in the rear of the train, and thus, cause the energization of the yellow lamp Y of signal 4.

Assuming the dispatcher to have operated the signal control lever l-8SGL to its right-hand position, the signal 8A or the signal 83, dependent upon the position designated for the operation of the track switch 3W, is cleared for governing further passage of the east bound train, and it is believed to be readily apparent from the description as it has been set forth how such signal is controlled in accordance with the picking up of the relay SRGZ in response to a control code transmitted from the control office. The picking up of the relay SRGZ, when the track switch 3W is in its normal position, closes a circuit for the relay 8AG (assuming the relay 8H for the track section 89T to be picked up) extending from including front contact HI] of relay 'I-STR, front contact III of relay 3NCR, back contact H2 of relay 3RCR, front contact H3 of relay 3RGZ, front contact H4 of relay 8H, and winding of relay SAG, to The picking up of relay SAG selects the energization of the lamps of signal 8A in an obvious manner by contact H5. If the track switch 3W is in its reverse position, the relay BBG is picked up by a circuit extending from including front contact H0 of relay 1-8TR, back contact III of relay 3NCR, front contact H6 of relay 3RCR, front contact H1 of relay 3RGZ, and winding of relay BBG, to

It will be noted that the shifting of contact H8 of relay fiAG upon the picking up of that relay for the control of signal 8A changes the code rate transmitted from right to left in the track section 5-11 from a code to a code, but in order that the relay 'ICP may be active for the transmission of a 180 driven code, the approach control relays SAAR and 8BAR must both be dropped away. This arrangement provides a check on the inverse code to provide that the signal 6 cannot provide a clear indication, even though the signal 8A is clear, if an inverse code is received at the right-hand end of the track section 6-7T so as to hold the approach control relay GAAR in its picked up position. Thus, there is a check provided that prevents the signal 8A from providing a more favorable indication than caution if the relay SAAR is held up by foreign current in the track section 6-1T when the inverse code is intended to be removed from that track section by the presence of an approaching train in the track section 4-5T. The principles of operation of this arrangement of a check on the inverse codes is more fully disclosed in the patent to F. X. Rees, Patent No. 2,353,930 dated July 18, 1944, to which reference can be made for a more complete disclosure. It is, therefore, provided that the relay TCP can become active for the transmission of a 180 driven code only when relays 8AAR and BBAR are both dropped away. The circuit for relay l'CP under such conditions extends from including back contact 22 of relay I'IR, oscillator contact I800, front contact H8 of relay BAG, back contact H9 of relay BBAR, back contact E29 of relay 8AAR, back contact 23 of relay 'IFBP, back contact 26 of relay IFZ, contact 25 of relay 'IFR. in its right-hand position, front contact 26 of relay 'IAS, and winding of relay 2GP, to

Change in direction of trafiic.To consider the mode of operation of the system when it is desired to change the direction of traffic, it will be acacia assumed that traific direction is established as illustrated in the drawings and. as heretofore described for east bound traffic and that the conditions of the system exist as they have been described when considering the normal conditions of the system, and as illustrated in the track diagram of Fig. 3A.

To initiate the change in trafiic direction, the dispatcher rotates the traflic direction button l-8FB in a counterclockwise direction and then depresses the button to initiate the transmission of a cycle of operation of the communication system to the field for initiating the change in the direction of trafiic.

When the button. I-8FB is rotated in a counter-clockwise direction the rotary contact of that button in combination with the depression of the button closes a'circuit for the upper winding of the relay l-BFL to cause'that relay to operate its polar contacts to their left-hand positions. The upper winding of relay l-8FL is energized under such conditions by a circuit extending from including back contact [2| of relay i-EGK, upper winding of relay I-SFL, contact R2. of the button l-SFB closed in its counterclockwise rotated position, contact 523 of button l-BFB closed when that button is depressed, and back contact I2 5 of relay ll-SGK to It will be noted that the energization of the circuit just. described can be eiiected only when the relays l-ZGK' and l-8GK' are operated to their d'ropped'away positions in correspondence with the stop indication of the signals governing entrance to the stretch of track between the passing sidings A and B; In other words, the relay i-BF-L operates its contacts in response to the operation of the button i-S'FB', only if the signals governing entrance to the stretch of track betweenthe passing sidings A and B are at stop.

The change relay CH2 ispicked up in response to the depression of the button. l-SFB by the.

energization of a circuit. extending from including contact 25 of button. I-BFB in its. depressed position, contact I26v of button l-SFB in. its counter-clockwise rotated position, windings of relay CH2, and normally closed contact.

22? of the cancel button CAN, to Relay CH2 is-maintained picked. up by its stick circuit which is closed at back contact I28 of relay LC2' until relay LC? is picked for the transmission of a cotm'ol. cycle to field station No. 2.

The picking up of relay C52 is eliective to initiate the transmission of a control cycle of. operation of. the code communication system for the transmission of. controlsv to field station No. 2 by the shifting of contact iii! to cause the picking up of relay LC2. in a manner specifically disclosed for the operation of the relay LCli shown in. Fig. 2A of the above-mentioned Hailes et al. application. The picking up of relay LCZ, as disclosed in that application, connects respective chamiels of the code communication system through switch and signal selecting contacts to the code determining relays. SL and LS. An additional channel wire No. E39 is used according, to the present invention for providing, a code character in the control cycle of operation for the control of a magnetic-stick relay FZ in the field. It is to be understood that the character used for the control of the relay FZ in the field may be suitably positioned in the control cycle in accordance with the requirements of practice tov either precedeor follow the characters used. for switch and signal control, and such char- T8 acter can be decoded at a field station in any suitable manner according to the requirements of practice, such for example, as in the manner specifically disclosed in Fig. 5 of my prior application, Ser..No. 655,622, dated March 19, 1946. Such figure shows specifically decoding means for positioning the contacts of a magnetic-stick traffic direction relay in response to the reception at a field station of. respective (LS) and (SL) cede. characters. Thus, for the purpose of simplification of the disclosure of the present invention, believed sufiicient to assume that the transmission from the control office of an (LS) character is effective to pick up. the relay FZ by the polarity of energization of its upper winding at the field station selected for the reception of controls, and the transmission of an (8L) character. is effective to cause the dropping away of the relay FZlby the polarity of energize;-

tion of the lower winding of that relay at the field station selected for reception of controls to cause.

that relay to be dropped away.

It is selected when considering a change in the direction of trafiic, that the code character transmitted to the field station No. 2 in the control cycle which has been described as being initiated by the picking up of relays CH2 and L02, is an (LS) character to cause the energization of the upperwinding of the relay EFZ at field station No. 2 to pickup that relay. More specifically, when energy applied, to the channel wire No. I38 during the transmission of the control cycle, the relay LS is pickedup by the energiza.-- tion of a' circuit-extending from the charmelwire No. we including'front contact E35 of relay L02, contact I32 of relay l-EFL in its left-hand position; back contact 633 of relay SFPS; and winding of relay LS to The picking up Oifl'lfiY- LS by the closure" of front contact 5535 selects an (LS) code character for transmission during the control cycle to the field station No. 2 for the control ofv relay ZFZ at that field station.

Upon the reception of the control cycle at field station No. 2; the LS character for the control of relayEFZ" (see Fig; 2A) causes energy to be applied tothe upper winding of that relay through a circuit including contact I35 of relay 2FR in its'right hand position. This arrangement provides that the relay ZFZ cannot bepicked up to interfere with code transmission when the code transmitter: relay 2GP is active for the transmission of' a driven code.

The picking up of relay Q'FZ' in responsefto. the control cycle of operation transmitted from the control o'fiice, closes a circuit to energize the lower winding of the traffic direction relay EFR to operate thecontacts of such relay to their lefthand positions: Such circuit extends from including front contact 6'36 of relay front contact 53? of'relay 2A5, and lower winding of relay 2FR' to- It will be noted that the inclusion offront contact 53? of relay EAS in that circuit checks that the signals in. and 2B are atstop and that the approach looking associated withsuch signals assumes its normalposition.-

In response to the shifting of'the contacts of relay'F-Pe to their left-hand positions, the opening of a circuit by contact E33 of relay EFR is effective to transmit an indication to the control .oflice' of the change-in the position of the con- :tacts of that traific direction relay, and the reception of such indication at the control o ifice is effective tooperate the contacts of the magnetic-stick relay ZFK to theirle ft-hand positions. Upon the operation of the contacts of relay ZFK to their left-hand positions, the stick circuit by which relay ZFPS has been maintained picked up is opened at contact 2i, and thus, the relay ZFPS. is dropped away. It will be more apparent as the description progresses that the dropping away of the relay ZFPS conditions a circuit at back contact I39 whereby the relay LS can be energized for the transmission of an (LS) character at some future time when it is desirable to again change the direction of traffic. It will be noted that the dropping away of relay ZFPS is not effective by the closure of back contact I48 to pick up the relay CH3 for the initiation of a control cycle for transmission to field station No. 3 because of the contact MI of relay 2FK being in its left-hand position. Thus, the relay ZFPS, and also the relay SFPS, is effective to automatically initiate the transmission of a control cycle only just prior to the picking up of that relay in a manner to be hereinafter described.

Upon the shifting of the contact I42 of the relay ZFR (see Fig. 2A), with the relay EFZ picked up, the relay 2GP becomes steadily energized to connect the track battery across the track rails of the track section Z-ET through front contact 6? of relay 2GP. The circuit by which relay 2GP is steadily energized under such conditions extends from including back contact 69 of relay 2TB, front contact I43 of relay 2FZ, contact I42 of relay 2FR, in its left-hand position, front contact Hi l of relay ZAS, and winding of relay 2GP, to

As a result of the steady energization of the track rails of the track section 2-3T, the track relay 3TB. (see Fig. 2B) at the right-hand end of the track section becomes steadily energized, and the relay 3FP is picked up, but the relay 3FBP remains in its dropped away position.

The picking up of the relay SFP, with the relay SFBP dropped away, closes a circuit for the traffic change relay S-GFC extending from including back contact I 35 of relay SFBP, front contact I 58 of relay 3F'P, contact I47 of relay 3-4FR in its right-hand position, and winding of relay 3-4FC to The relay 3-4FC has slow pickup characteristics so as to insure that the particular combination of the picking up of the relay 3FP with the dropped away relay 3FBP is in response to the steady energization of the track rails rather than to a condition involving the establishment of track circuit code in that track section as after the passage of a train.

In response to the picking up of relay 3- iFC, the circuit for relay S-dH is opened at back contaot I48 to cause that relay to be dropped away, and also the stick circuit by which the relay B- iFS has been maintained picked up is opened at back contact to cause that relay to be dropped away after its picked up circuit is opened at front contact I49 of relay 3-4H.

With the relays 34H and 3- 3FS dropped away, a circuit is closed by which the upper winding of relay S- lFR is energized with a polarity to operate the contacts of that relay to their lefthand positions. Such circuit extends from including back contact I49 of relay 34H, back contact 53 of relay 3-4FS, front contact I5I of relay 3FP, back contact I52 of relay SFBP, front contact I53 of relay B-GFC, and upper winding of relay 3-4FR, to The shifting of contact I l'I of relay siFR opens the circuit by which relay 3-4FC has been energized, and causes the dropping away of that relay. Relay 3-4FR, is maintained with its contacts in their left-hand positions by its magnetic-stick characteristics.

Although the relay has been rendered inactive upon the reception of the steady energization at the right-hand end of the track section 2-3T by the opening of its circuit at back contact E2 of relay 3TB, the shifting of contact I56 of the relay fi-QFR in the circuit for relay 3GP prevents further transmission of drivencodes by that relay and conditions that relay so that it can be used for the transmission of an inverse code for approach control purposes.

Upon the shifting of contact I8 of the relay 3- iFR to its left-hand position in the circuit for relay iCP, a circuit is closed to pick up relay 6GP for the steady energization of the track rails at the left-hand end of the track section 4-51. The circuit by which relay 4GP is steadily energized under such conditions extends from including back contact 52 of relay 4TB, back contact I54 of relay SFBP, front contact I55 of relay QFP, contact 18 of relay 3-4FR in its left-hand position, and winding of relay 4GP, to The closure of front contact 50 upon the picking up of relay dCP applies steady energy from the track battery I56 to the track rails at the lefthand end of the track section i-5T.

At the right-hand end of the track section -5T, the reception of the steady energy, as compared to the inverse code which has been received at that end of the track section, causes the dropping away of the relay 5FBP (see Fig, 20) because of the steady energizing of the track relay STR, and thus closes a circuit for the slow pickup relay 5-6F'C. Such circuit extends from including back contact I5! of relay 5FBP, front contact I58 of relay 5FP, contact I59 of relay E-tFR in its right-hand position, and winding of relay E-SFC, to

The picking up of relay 5-6FC causes the dropping away of relay 5-61-1 by opening its circuit at back contact 38, and the relay 5-6FS is dropped away upon the dropping away of relay 5-6H because of the opening of its stick circuit upon the picking up of relay 5-5FC and its pickup circuit at front contact I50 of relay 5-51-1.

Upon the dropping away of the relay 5-6FS, a circuit is closed for energizing the upper winding of the relay 5-SFR with a polarity to operate the contacts of that relay to their left-hand positions. lhe circuit by which the upper windin of relay E-SFR is energized extends from including back contact I60 of relay 5-6H, back contact It! of relay 5-5FS, front contact I52 of relay EFF, back contact IE3 of relay EFBP, front contact I of relay S-SFC, and upper winding of relay E-SFR, to The shifting of relay 5-6FR causes the dropping away of relay E-SFC, and the dropping away of that relay opens the circuits for both windings of relay E-EFR at front contact I54 and I65.

Although the code transmitter relay 5GP has been rendered inactive for the transmission of driven codes from right to left in the track section 4-51 by the steady energization of relay 5TB and the opening of its circuit at back contact 53, the shifting of contact d1 of relay B-BFR to its left-hand position conditions the relay 5GP for the transmission of an inverse code for use in approach control when the driven code transmitter is rendered active at the left-hand end of the track section 4-5T.

The relay 6GP is steadily energized to apply steady energy to the track rails at the left-hand end of track section B-IT through front contact 29 in accordance with the energization of a circuit closed upon the shifting of the contacts of relay -6FR. The circuit by which relay 6C? is energized under such conditions extends from including back contact 32 of relay GTR, back contact 36 of relay EFBP, front contact I87 of relay 5FP', contact 81 of relay 5-6FR in its left-hand position, and winding of relay 6GP, to

The reception of the steady energy at the righthand end of the track section fi-lT maintains the track relay lTPt (see Fig. 2D) steadily picked up, and thus causes the dropping away of the relay 'IFBP. The dropping away of relay TFBP closes a circuit for the slow pickup relay 'EFC extending from including front contact H58 of relay 'lFP, back contact I69 of relay 'IFBP, contact Hi3 of relay l'FR in its right-hand position, and winding of relay l'FC, to In response to the picking up of relay 'iFC, the upper winding of the relay 'dFR is energized with a polarity to operate its contacts to their left-hand positions. The circuit by which relay 'EFR is energized extends from (-1-) including front contact Hi8 of relay lFP, back contact it!) of relay 'iFBP, front contact iii of relay IE0, and upper winding of relay 'EFR, to The shifting of contact ilii of relay lFR causes the dropping away of relay i'F'C, and the dropping away or" that relay opens the circuit for the upper winding of relay TFR at front contact ill Upon the shifting of the contacts of relay 'EFR to their left-hand positions, the circuit by which the relay lCP has been active for the transmission of driven codes is opened at contact 25, but such relay has been rendered inactive by the opening of its circuit at back contact 22 upon the steady energization of the track relay iTR.

Having thus checked that the stretch of track is unoccupied by a train with a condition of steady energization applied to the entrance end of each of the track sections in the stretch, the operation of the contacts oi the relay lFR, to their left-hand positions is an indication that the stretch of track is unoccupied, and such indication is communicated to the control o'ifice by the code communication system in accordance with the closure of contact N2 of relay lFR in its left-hand position. The indication transmitted in accordance with the closure of contact H2 of relay lFR in its left-hand posi-- tion is effective at the control ofiice to operate the contacts of the magnetic-stick relay SFK (see Fig. 1) to their left-hand positions.

Upon the operation of the contact N3 of relay SFK to its left-hand position in response to the reception of an indicationthat the stretch of track is unoccupied by a train, a circuit is closed to energize the relay CH2 for initiating the transmission of a control cycle to field station No. 2. The circuit by which relay CH2 is energized under such conditions extends from including back contact H t of relay SFPS, contact N3 of relay 3FK in its left-hand position, winding of relay CH2, and normally closed contact 1210f the cancel button CAN, to The picking up of relay CH2 causes the picking up of relay L02 at the beginning of a control cycle for the transmi sion of controls to field station No. 2. When the relay L02 has been picked up, subsequent to the shifting of contact N5 of relay SFK to its lefthand position, the relay tFPS is picked up by the energization of a circuit extending from including front contact NE of relay L02, contact N5 of relay SFK in its left-hand position, and winding of relay tFPS, to A stick circuit is closed for relay 3FPS at front contact I11 including contact N5 of relay in its left-hand position to maintain that relay picked up until another change in the direction of traffic is effected. The picking up of relay SFPS opens the pickup circuit that has been described for relay CH2 at back contact lid to cause the dropping away of that relay.

As has been pointed out when considering the general mode of operation of the system, the purpose of automatically irntiating the communication system into a cycle of operation for the transn-i-ission of controls to field station No. 2 is to remove the condition of steady energization of the track rails that hasbeen applied to the left-hand end of the stretchof track between the two passing sidings, and initiate the transmission of driven code at such end in the direction required for the control of signals governingwes't bound trafiic. It is the purpose of the control cycle described as having been initiated, to transmit a control to field station No. 2 for the energization of the lower winding of the relay ZFZ (see Fig. 2A) with a polarity to cause such relay to be dropped away. Thus, havingdescribed the relay ZFZ as having been picked up initially by the transmission of an (LS) character, an (SL) character is transmitted for the dropping-away of the relay ZFZ during the cycle of operation under present consideration.

The relay SL is picked up during the control cycle in response to the application of energy to the channel wire No. 539 for effecting the transmission of an (SL) character by the energization of a circuit extending from the channel wire N0. iSii including front contact E3! of relay L02, contact 832 of relay i-BFL in its left-hand position, front contact 538 of relay SFPS, and winding of relay SL, to The application of energy at field station No. 2, upon reception of the above-described trailic control, to the wire ilii' by the decoding circuits of the communication system, causes energization of the lower winding of relay EFZ with a polarity to cause that relay to be dropped away.

Upon the dropping away of relay 'EFZ, the circuit by which the relay 20? has been steadily energized is opened at front contact Hi3, and the closure of back contact Ms renders the relay 2GP active for the transmission of a driven code in accordance with the contact M2 of relay ZFR being operated to its left hand position Thus, the relay 2GP becomes active to transmit a driven code -(assuming the signal EA to be at stop) by the energization for each pulse of the code of a circuit extending from including back contact 69 of relay 2TH, oscillator contact 150, front contact N9 of relay ZAAR, back contact I89 of relay ZFBP, back contact I43 of relay 2FZ, contact E2 of relay ZFR in its left-hand position, front Contact Me of relay EAS, and winding of relay 2GP, to

The pulsing of contact ill of relay 2GP applies code pulses at a 75 rate to the track rails of the track section 2-3'1, and the reception of such pulses at the right-hand end of that track section causes the relay 3TB. (see Fig. 215) to follow the code. The relay 3F]? is maintained picked up, and the relay EEFBP is picked up in accordance with the pulsing of the contact l8i of relay 3TB.

Inasmuch as the relay E- lFR has had its contacts operated to their left-hand positions, the relay E-ETP is selected to follow the coding of contact 62 of relay 3TB, such relay being rendered active in accordance with the closure of front contact I' 82 of relay EFBP. The pulsing of contacts 55 and 56 of relay S-ATP provides for the picking up of the relay fiiH in a manner which has been described, and the yellow lamp of signal 3 becomes energized in accordance with the picking up of relay 34H by a circuit extending from including contact 53 of relay 3-4FR in its left-hand position, front contact [83 of relay 3-4H, back contact 584 of relay S-QD, and the yellow lamp Y of signal 3, to It will be noted that the signal 3 is selected in preference to signal 4 by the shifting of contact 58 of the traflic direction relay 3-4FR upon changing the direction of traffic, thus, the lamps of signal 4 are all deenergized when the direction of trafiic is established for west bound trains.

The relay 3-4FS has its pickup circuit energized upon the picking up of relay 3-41-1 by the closure of front contact M9, and the picking up of that relay establishes its stick circuit which is maintained closed dependent upon back contact 9d of the relay 3-4FC. It will be noted that the relay 3-4RS must be picked up before the relay ECP can be rendered active for the transmission of a driven code in the track section -51 because the front contact 94 of relay S- iFS is included in the circuit for rendering the relay 40? active as a driven code transmitter. It is, therefore, provided by this circuit organization that the rendering active of the relay iCP initially, subsequent to a change in trafiic direction, is dependent upon the reception of a track circuit code at the right-hand end of the track section 2-31.

This organization of the system provides that even though the trafic direction relay 3-4FR at the intermediate signal location can be operated to change direction of traffic by the application of steady energy to the track rails of the track section 2-3T under abnormal conditions, as by a signal maintainer in testing circuits, the code transmitter relay 4GP cannot be rendered active unless a traffic direction control is transmitted from the control ofiice in accordance with the newly selected direction of traffic for initiating the driven code transmitter at the left-hand end of the stretch of track to provide that the relay 3-4H is responsive to a track circuit code, and by its picking up, a pickup circuit is closed by which the relay 3- lFS can be picked up to render the code transmitter relay ECP active. It is believed to be readily apparent that a similar mode of operation is effective at the intermediate location of signals 5 and 6, and for a change in traiiic direction to set up the opposite direction of traffic to that which has been specifically considered.

Upon the picking up of relay 3- iFS in response to the reception of track circuit code at the righthand end of track section 2-31, the relay 50? is rendered active for the transmission of a 180 code, the circuit which has been described by which the relay 4GP has been steadily energized having been opened at back contact 45d of relay SFBP upon the picking up of that relay. The circuit by which the relay is energized for each pulse of the 180 code extends from includin back contact 52 of relay lTR, front contact M of relay 3-4FS, oscillator contact iiisC, front contact I85 of relay 34H, front contact 554 of relay EFBP, front contact I55 of relay 3FP, contact E8 of relay 3-4FR in its left-hand position, and winding of relay QCP, to

The pulsing of contact 5d of relay 4GP applies code pulses to the track rails of the track section 4-5T at a 180 rate, and the reception of such pulses at the right-hand end of that track section renders the relay 5TB (see Fig. 26) active to follow the code. The pulsing of contact 8! of relay 5TB. provides for the picking up of the relay 5FBP. Upon the picking up of relay EFBP, the track repeater relay 5-5TR is rendered active to repeat the code pulses by the energization of a circuit for each pulse extending from including front contact 43 of relay 5TB, front contact 86 of relay EFBP, contact 34 of relay 5-6FR in its left-hand position, and winding of relay S-STP, to The pulsing of the contacts 35 and 35 of relay 5-51? is effective to cause the picking up of relay 5-5H and 5-5D, and the picking up of such relays provides for the energization of the green lamp of signal 5 by a circuit extending from including contact 39 of relay E-EFR in its left-hand position, front contact 81 of relay 5-6H, front contact 188 of relay 55D, and the green lamp G of signal 5, to

The relay 5-6FS is picked up in response to the picking up of the relay E-SH when code is received at the right-hand end of the track section 4-5T by the energization of an obvious circuit closed at front contact 16%, and the picking up of that relay establishes its stick circuit which is maintained closed at back contact 26 of relay 5-6FC until the relay 5-6FC is again picked up upon another change in the direction of traific.

The circuit by which the relay 8GP has been steadily energized is opened upon the picking up of relay EFBP, and the relay 60? becomes active to transmit a driven code in accordance with the relay 5-6H being picked up in response to the reception of a track circuit code through the track section t-ET. The circuit by which the relay 6GP is rendered active for the transmission of a driven code is closed upon the picking up of relay 5-5FS and extends from including back contact 32 of relay 6TB, front contact 83 of relay 5-6FS, oscillator contact 188C, front contact I89 of relay 5-5H, front contact H56 of relay 5FBP, front contact l6? of relay 5FP, contact 87 of relay 5-5FR in its left-hand position, and winding of relay 5GP to The pulsing of contact 25 of relay EECP applies driven code pulses to the track rails of track section 6-7T at a 180 rate, and the reception of such pulses at the right-hand end of that track section renders the track relay 'ITR (see Fig. 2D) active to follow the code, and thus provides for the picking up of the relay 'IFBP by the pulsing of contact 88.

The pulsing of contact 22 of relay 7TB causes the relay 'ITP to become active by the energization of a circuit extending from including front contact 22 of relay 'lTR, front contact of relay lFBP, contact 19! of relay TFR in its lefthand position, and winding of relay lTP, to and the pulsing of the contacts l5?! and I93 of relay lTP at a 180 rate, with the contacts of relay TFR in their left-hand positions provides a means through the decoding transformer for picking up the relays 1H and ID to provide for the clearing of signal 1A or signal 7B in response to the transmission of a signal control from the control office for clearing either of such signals. Thus, for example, if the dispatcher transmits a control cycle of operation to the field station No. 3 calling for the track switch 3W to be in its normal position and the signal '!A to be clear, the picking up of the relay 3LGZ in response to such cycle of operation closes a circuit for the energization of relay TAG extending from including front contact III] of relay 'I-BTR, front contact H I of relay 3NCR, back contact I I 2 of relay 3RCR, contact I94 of relay TFR in its left-hand position, front contact I95 of relay BLGZ, front contact I96 of relay TH, and winding of relay TAG, to The picking up of relay FAG opens the circuit by which the red lamp R of that signal has been energized at back contact E91, and closes a circuit for the green lamp (3- of that signal extending from including front contact IQ! of relay TAG, front contact I93 of relay 1D, and the green lamp G of signal 1A, to

The establishment of inverse code transmission through the track sections 2-3T and i-T for approach control associated with the signal I A is comparable to the manner which has been heretofore described in which the transmission of inverse code through the track'sections i-ET and B -IT is effective for providing approach control for the signal 8A. Thus, the relay E-ETPA (see Fig; 2C) is active for the transmission of an inverse code by the energization for each pulse of the inverse code of a circuit closed upon the dropping away of the relay 5TB and extending from including back contact 13 of relay 5TB, front contact 44 of relay S-EFS, front contact I99 of relay SFBP, contact 85 of relay ti-tFR in its left-hand position, back contact 85 of relay 5-5TPA, contact 47 of relay E-GFR in its lefthand position, and winding of relay 5GP, to The relay 5-5TPA is energized at the same time,

and the picking up of such relay after a time delay provided by the variable inductance 20!! terminates the inverse code pulse upon the opening of back contact 86.

The reception of the inverse code at the lefthand end of the track section 4-5T when the system is established for west bound traffic provides for the relays dFP and lFBP to be picked up, and the picking up of relay 4F? is effective to render the relay 3GP active for the transmission of an inverse code in the track section 2-3T. The circuit by which the relay 3GP is active for inverse code transmission under such conditions extends from including back contact 62 of relay 3TB, front contact 63 of relay S- SFS, front contact 80 of relay QFP, front contact 201 of relay SFBP, contact N3 of relay 3- iFR in its lefthand position, back contact ll of relay 3- lTPA, contact 66 of relay S-QFR in its left-hand position, and winding of relay 3GP, to

Having thus described in detail the mode of operation of the system upon a change in direction or" traiilc from a direction originally set up for east bound traffic to the direction set up for west bound traific, inasmuch as the system is symmetrical in its operations for a change of traffic in either direction, it-is believed to be readily apparent from the description as it has been set forth that a similar mode of operation is effective to change the direction of trafiic from traffic set up for west bound traffic to a direction of traflic for the passage of east bound trains.

It will be noted that the above described specific mode of operation of the system bears out the general description as it has been set forth with respect to the mode of operation of the system uponreversal of traffic in that a single manual designation of trafilc reversal at the control office is; all that is required to cause the transmission of a-r-control to the entrance end of the stretch, according to the last established direction of traffic, for the applicationrof steady: energy to the track rails such stretch of track is unoccupied by a train, and the reception of such indication at communication system for transmitting a control to the entrance end of the stretch, according to the last established direction of traiiic, for the removal of the condition of steady energization from the track rails, and the initiation of driven code transmission for the control of signals governing the direction of traffic which has been manually designated by the dispatcher at the control office.

It is believed to be apparent from the description as it has been set forth that if the condition of steady energization fails to be transmitted from one end of the stretch to the other because of the presence of a train at an intermediate point, there is no indication transmitted to the control office for operating the relay FPS (see Fig. 1) associated with theexit end of the stretch, according:

to the last established direction of traflic, and therefore, such relay upon remaining dropped away, selects an (LS) character for the transmission to the field station No. 2 for any cycle of operation for the transmission of controls thatcan be manually initiated by the dispatcher. Thus, it is provided that even though the dispatcher manually initiates the code communication system into a cycle of operation for the transmission of controls to field station No. 2, he cannot in any way designate a control for transmission that will remove the steady energization from the end of the stretch corresponding to the entrance end for the last direction of trafiic, and establish the transmission of driven code for the newly designated direction. By this arrangement it is provided that a reversal in traffic direction as for the back-up movement of a train when a train occupies the stretch of track cannot be accomplished. This feature of the system is desirable under certain conditions to be encountered in practice as compared to a system allowing back-up train movements as in my prior Patent No. 2,357,519, dated Septemberb, 1944.

It has been pointed out that the approach control of the leaving signals at the ends of the stretch is dependent upon the combined operations of the relays AAR and BAR in such a manner that an indication is transmitted to the control office that the associatedapproach section is occupied by a train only if both relays are' dropped away; and similarly, the dropping away of both of the relays is required to prevent the approach release-of the looking for the leaving signal at the end of the stretch with which such relays are associated.

Generally speaking, the relay AAR at each end ofthe stretch is energized in response to the inverse code provided for approach control, while the relay BAR is energized at each end of the stretch when such end is an entrance point with respect to the stretch and an inverse code is not transmitted through the coded track circuit at that end. In such a case, the relay BAR is energized in response to the driven code transmitted through the track rails to that end of the stretch. Although .each relay BAR is shown as being energized in response to either code rate, it is to be understood that it can be ener gized only in response to a code if it is'desired to extend occupancy detection for another track section.

It will be readily apparent that provision must be made for preventing the momentary deenergization contemporaneously of the relays AAR Thus, it is provided that. 

